"But if you're fair dinkum get rid of the carbon tax ... (and) return to the border protection policies that worked rather than the 'if you can get here you can stay here' policies which the Greens have foisted on this government."

The opposition leader dodged three questions about whether he'd rather deal with Julia Gillard or Kevin Rudd as Labor leader.

Both of them had strengths and weaknesses, Mr Abbott said.

"I don't really think it's my job giving public advice to the Labor Party when it comes to their own leadership," he said.

Meanwhile, Prime Minister Julia Gillard is doubtful the Greens will side with the coalition to vote against her jobs package in parliament.

The Greens say if the federal government doesn't fix the revenue holes in the mining tax, it won't support Ms Gillard's plan to axe research and development tax breaks for big companies.

The $1 billion savings measure is supposed to pay for the government's "game-changing" jobs and innovation package as well as deliver money to budget bottom line.

Greens leader Christine Milne, who severed the minor party's alliance with Labor this week, said the decision to block the R&D cuts showed "the difference between having an agreement with Labor and not having one".

Ms Gillard questioned whether the Greens really would vote against jobs and ending tax cuts for some of the richest companies in Australia, including resource firms.

She argued the Greens could only block the package if the opposition decided to vote against it in parliament.

"The Greens only matter if (Opposition Leader) Tony Abbott directs his team to come into parliament and vote against Australian jobs," Ms Gillard told Adelaide's 5AA Radio today.

"I know Mr Abbott and his team have been saying they will do that."

Often the "positioning and stalking around" legislation never materialised when it came to the vote in parliament, she added.

Environment Minister Tony Burke said the Greens had opposed every one of the government's attempts to make major environmental reform simply because it didn't match their desired outcome.